Tuesday, April 5, 2016

Another two failures, one fixed by reset

Back in February I found that the Behringer DCX 2496 digital crossover had failed. It wasn't turning on at all. I was very busy at the time, so I decided to go two weeks before setting up a spare unit I had on hand. Meanwhile I could listen to the Acoustat 1+1's full range.

I didn't like the full range sound. Very lacking in bass.

But then as I was setting up the spare DCX, I discovered that the DEQ 2496 I was using for the Acoustat crossover (80Hz to 20kHz) wasn't working properly. Regardless of settings, even if I had all parametric EQ's turned off so it couldn't possibly be crossing over, it was rolling off the bass around 300 Hz.

So this means my assessment of the "full range" of the Acoustats was possibly in error.

However I was able to fix the DEQ simply by re-loading the "default" settings and then reprogramming it. It hadn't actually died, it had gotten confused.

Programming the DEQ for a Linkwitz-Riley 24dB/octave filter is easy once you've figured it out. Basically one must use the "LC" parametric setting at the crossover frequency, and then dial the cutoff to -15dB. But that -15dB is not really correct, it really keeps rolling off as far down as I've been able to measure at 12dB/octave. Putting two LC's together gives 24dB/octave rolloff, with -6dB at the specified frequency, exactly as Linkwitz-Riley requires. The L12 and H12 parametric settings don't work well for this.